Used motor oil has been known for many years as a metal preservative and has had very limited use as a rust inhibitor on oil drilling equipment, the protection of farm machinery, etc. The effectiveness of the used oil has previously been attributed to the thickening resulting from the accummulated contaminants which keep it from soaking in and from evaporating. However, there has never been any widespread use for these contaminated oils. Rather, there have been numerous problems associated with such efforts. For example, the relatively high cost of collecting a large number of small quantities, the ultimate disposal of unwanted material by methods compatible with environmental protection, etc., have not found economic justification.
In recent years some small scale re-refining methods have been put into operation in which marketable oils are recovered. However, due to the high costs involved and the resulting narrow margin of profit, such recovery methods represent a small percentage utilization of the total quantity of used motor oils.
A much larger utilization of used lubricant consists of treatment with acid, etc. to partially clean it so that it may be blended with fresh oil and burned as fuel. However, such utilization destroys valuable lubricating and corrosion inhibiting components at much less valuable fuel oil price levels.
The ever increasing scarcity and consequent high cost of petroleum, particularly high quality lubricating stocks, now presents positive incentives to selectively remove undesirable contaminants from used motor oils and reuse the valuable high quality lubricating components contained in such oils. A process has now been discovered whereby this may be accomplished in an economical manner.